Method of grinding spline shafts and other interrupted cylindrical bodies.



F. A. WARD. METHOD OF GRINDING SPLINE SHAI 'TS AND OTHER INTERRUPTEDCYLINDRICAL BODIES. APPLICATION FILED AUG-l3. 1912.

l ,271 ,495. h Patented July 2, 1918.

2 SHEETS-SHEET I.

INVENTOR F. WARD.

METHOD or GRINDING SPLINE sums HER INTERRUPTEYD CYLINDRICAL BODIES.

APPLICATIO AUG. 13, IQIZ- 1,271,495, Patented July 2, 191,8.

EETSSHEET 2.

3 141mm to:

FREDERICK ALEXANDER W RD, OF DETROIT, MICHIGAN, AssIeNoIt To GEAR GRIND-LNG MACHINE COMPANY, OF DETROIT, MICHIGAN, A CORPORATION OF MICHIGAN.

METHOD OF GRINDING sPLINE SHAFTS AND QTHER INTERRUPTED GYLINDRICALBODIES.

Specification of LettersPatent.

Patented July 2, 11918.

Application filed August 13, 1912. Serial No. 714,810.

T at! whom it mag concern:

Be it known that I, FREDERICK A. WARD, acitizen of the United States'ofAmerica, residing at Detroit, in the county of Wayne and State ofMichigan, have invented certain new and useful Improvements in Methodsof Grinding Spline-Shafts and other Interrupted Cylindrical Bodies, ofwhich the following is a specification, reference be:

ingha'd therein to the accompanying draw' lIlgS.

My-invention aims to provide certain improvements in the production orin the grinding of'splined shafts and other inter-.

rupted cylindrical bodies.

In the present state of the art in various structures such for instanceas sliding gear v transmission mechanism, it is found' desirabletoemploy spline shafts having integral keys or splines, and these partsare either heat-treated or left soft. One method of forming suchstructures is to machine the soft or annealed metal to the proper formand then to harden the same, but inthis "it'is extremely diflicult tosecure accurate work on account of the slight warping or change in formdue to tempering. Thismethod is alsoapplicable todsoft shafts that canbe roughly fashioned'and then finished by this 30 device to greateraccuracy than with a finishing tool. On the other hand it is impossibleto grind the shafts by the usual method of placing them in a grindingmachine as the splines interrupt the continuity of the cylindrical orother curved surface.

The present invention overcomes the difficulty by the novel method ashereinafter set forth.-

In the drawings: 4

Figures 1 and 2 are diagrammatic sec-' tions illustrating the operationsof trimming the grinder;

Fig. 3 illustrates the grinding of the spline shaft with the accuratelyformed grindlng medium;

4 Fig. 4is a diagrammatic side elevation of a machine on which the workand trimming mechanism is located; and Fig. 5 is, a perspective view ofthe completed work. Fig. 6 is asection of a shaft with a segment of asliding gear thereon.

Fig. 7 is a transverse section showing a comparison between the outlinesbefore and after grinding.

Which fashion the sides preferably aecomwished by a separate tool Thearticles which are fashioned by my improved grlndlng process consistessentially of longitudinally extended bodies havsimilar purposesconsist of cylindrical (HSlQPy;

the term cylindrical generically as including other curves than thearc,of a circle) forms, adapted to exactly fit corresponding cylindricalbores in the gears or other slid able members withone' ormore projectingsplines interrupting the continuity of these curved surfaces andfashioned to exactly fit the key seat in the slidable member, As shown,A is a spline shaft provided with four splines B distributed about theaxis at equal angles. Intermediate the splines are cylindrical segmentsC, while the sides D of the splines are parallel to each other and arepositioned to give an exact thickness.

My improved method of indin such articles consists essentially"; rst, intrim, ming a grinding medium into exact eonformity to one side 'orscgmentof the finished. structure; and in then alternately rei ingraduallyadjusting the grinder'toward the work or vice versauntilthe'latter isrev ducedlo finished size.- During this operation thegrinder is restored to form as frequentlyas found necessary tomaintainits form and the fashioned surface as finished includes thesidesof the splines as well as the cylindrical or curved segments.

In Fig. 1, the operation of trimming the segmental surface of thegrinder isillustrated, this being accomplished .by a pivotedtrimmingtool E provided preferably with a diamond point F and of aradius exactly corresponding to that of the finished work.

The tool E may be mounted upon the work table or bed G in alinement withthe centers Hon which the work is mounted, and thus after trimming ofthe grinder it may be en gaged with the work in precise relativepositlon.

The trimming of the grindingv surface the. splines, is

holder 1 hailing angling sides corresponding to the angles of thefinished Work and adjustable trimmer points J which may be reciprocatedon said sides to trim the wheel One of the centers H on which the worklationship with each other, and the one or,

the other is alternately reci )rocated in a longitudinal direction witht c axis of the work, and the work is rotatively adjusted respectivelyby the operation of the index-' iug mechanism 1, Thus instead ofgrinding each side to finished size before operating upon another--side, the same grinding cut is taken successively over all the sides.before any change in ad ustment for another cut. This sequence ofoperation has the advantage first that the heating efiect pro duced bygrinding is uniformly distributed over the shaft, which prevents anywarping action, and secondly, it permits the operator to graduallyreduce-the work to finished size, testing from time: to time with amicrometer or other gage.

Before the final cutreducing the Work to size the grinder medium ispreferably reformed so as to impart to the finished work the exact-formas predetermined;

Throughout the specification and claims the term cylindrical is usedgenerically to include non-circular as well as circular bodies.

In a previous patent of myself and Taylor No. 1,104,589 there isdisclosed a method ofgrimling the teeth of gears by means of agrimliug'wheel which passes between the leelll. Such grinding of tliegears for automobile transmissionsand the like has been practised fors'ome'years prior to this application and has produced a suhstantial'improvement in such transmissions. lint a satisfactory shaft for thesliding gear has not been available prior to this invention. Splinedshafts were defective bccause'ii hardened by heat treatment they werealuays badly distorted. and if not so her- (lened they were soon worn ortheir surfaces injured by the sliding of the hardened gears thereon. inthe best transmissions resort was had to square shafts hecaus'etheseafter heat treatment could be ground on their fiat faces by chi andknown methods. These are objectionable for two reasons; first, theyrequire; a corrcspondiugly square hole .Withgronndfaees through thehill) of thegear ulnch is expensive and diffie'ult to make and,

.wconchllie bearing surfaces of the gear of an inch or less.

' tor of the shaft.

ribs must also he spliued portionof curately spaced as to make on theshaft are at an extreme an le to lldh line oi: pressure in the rotationo the gem in use; whereas with a splined shaft, the, gear hub has around hole through it which can be easil ground with great accurac andthe re is (or approximately radial sides of the splines provide aperfecthearing surface normal to the direction of pres.- sure of the gear onthe shaft during rota-- tion. 3

.Splined shaftswere also used which were hardened and ground on thecylindrical faces of the splines because such faces could be ground onthe well known 'cylim drieal grinding machines, but the bottoms of thebroached grooves in the gear hubs could not be commercially groundand'without this an exact hearing on the outer faces of the splinescould not be secured. -But there was no known way of making splinedshafts which should be as hard-as the gears sliding thereon and shouldhe exactl straight and true to dimensions and which should provide abearing surface onthe por-' trons oi the shaft between thesplines.

In splined shafts, the sides of the space (flanks of the splines) arefiat and the distance between them must he maintained rigidly to preventlooseness of the gear, which would injure the sliding bearing surfaces.In good practice the spacing of such flanks from eacli'other is heldWithin a thousandth And the bottom of the groove between splines must beaccurately shaped and. located with respect to'the cen- The flat sidefaces of the carried down to the circular line of the hottoins oi? thegrooves. Furthermore the exactness referred to musthe maintainedthroughout the length ofthe ency of a shaft to bend in the length duringits cutting and heat treatment is a matter known to skilled persons inthis art.

Fig.- 6 illustrates the relations between a shaft A and a gear J havinga hub K sliding thereon. The ground bottoms L of the grooves on theshaft are fitted exactly to the corresponding ground faces M of the gearhub, and the our i'aces L are equidistant from the center of the shaft.The fiat faces -10 of the splines are ground and so sofit with thesitloshl' of the broached grooves in the gear hub. The outer faces 9 ofthe splines are clear of the opposed faces of the hub and need not beground.

i believe that such a splines] shaft itself,

hardened by heat treatment-or otherwise made so hard that it cannot becut to shape, and then shaped by grinding to produceb ariug facesliuccurately shaped and syncmetrically located with reference tothe-axis. and this throughout its length, is new; and

the shaft, and the tendf plane of its a perfect sliding 4 i with theside bearing surfaces D' ground to. make thr; splines eparatZy the circar faces of the she,

that it is furthernew to pi 'ovide such a shaft flat and straight fromall to end and from them in ooves in e shaft rubbing or by grinding withloose abrading material 'placed between the shaft and a gear which hasbeen shoved back and forth on the shaft until 'a sufficiently loose fithas been secured. Besides being terribly slow and expensive this methodhas not produced a straightshaft or one of uniform diameter or of exactconcentricity with its axis throughout its length. See Fig. 7, where Ais the finished shaft and P indicatesin dotted outline the cross-sectionat this point before grinding. Suppose this section takenat the pointwhere the distortion by heat treatment has producedthe greatesteccentricity. According to my process all the faces L and'D are grounddown to an exact radial distance from the trueaxis Q andlin exactangular relation with each other throughout the length of the shaft,even though at one cross-section the outline is at P and at an othercross-section 1n some other posltlon; and thls lnvolves, of course,leaving on the shaft before-hardenin suflicient' stock for thesubsequent grinding-operations at all points. But in the hand rubbingand similar operations referred to the shaft has? been milled or hobbedto final size and heat treated with the greatest care to minimizedistortion andthen such shafts as did not slide freely through a testgear were rubbed or ground merelyto remove the high spots here andthere,producing a shaft always small enough, generally too small at oneor more points along its length and almost never quite straight and truewith relation to its axis of revolution.

The member which is mounted on .the

fsplined shaft may be not only a gear, as

above described, but any one of various other devices whose center hasto coincide accurately with the central axis of the shaft on which itiscarried. And while the invention is of articular'value in the caseofmembers w ich have a sliding fit and are intended in operation'to slideon the shaft, it is of great value also where the member is mountedat afixed pointjiii the length, of the shaft, as for example, by a pressfit. In

the case ofa sliding or a non-sliding gear or other member, theimportant point is to locatelthecenter of operation of such a member onthe axis of rotation ,of the shaft,

on the and this is perfectly accomplished by the I accuracy with whichthe bottoms of the grooves on, the shafts and the complemengear can .be

parallel to the axis of the former, said wheel being provided with aconcave ei'ipheral surface of exactly predetermined arc cor-- respondingin radius to that of the finished cylindrical surface and of a lengthcorresponding to that between the obstructions in the finished surfaceof the work, and also provided with a fashioned surface at the edge ofthe concave portion for grinding the face of the obstruction;rotating-the work to a series of exactly predetermined positionsintermediate reciprocations to present different segments to thegrinding actionand re-trimming the surface of said grinder to restoreits exact form prior to'the finishing cut.

2. The method of grinding obstructed cylindri'cal surfaces, com risingmounting the work and 'a grinder wlieel in an organized work-grinding,machine, adapted to relatively reciproca the one in relation to theother and parallel to the longitudinal axis of the work; trimming saidwheel' while thus mounted to.v form a concave peripheral surface ofexactly predetermined arcv corresponding in radius to that of thefinished cylindrical surface, and of a length corresponding to thatbetween the obstructions in the finished surface of the work, and alsohaving .a fashioned surface at the edge of the concave surface forgrinding the face of the obstruction; and rotating the work through aseries of exactly predetermined positions to present different segmentsto the grinding action. a

3. The method of producing a shaft which vconsists in forming the sameof hardened steel with projecting splines and intermediate groovesbetween the splines; leaving stock for grindin throu bout the splinedportion, and grin ing wit a formed wheel bearing faces on the bottoms ofsaid grooves thou hout their length and width and symmetrlcally withreference to the axis of the shaft. v

' 4. The method of producing a shaft which consists in forming the sameof hardened steel withprojecting splines and intermediate groovesbetween the splines, leaving'stock for grinding throughout the splinedportion, gr'indin fiottoms of said grooves throughout witha formedwheelbearingfaces their length and width and symmetrically withreference to the axis of the shaft, and by momma of said formged whee];grinding the flanks of the spliges parallel to tho axis mo straight fromendto end and from their bottom (to their @011 edges.

5. Themethod. of producing-ashaft which consists in forming the some. ofhaflfieno steel with projecting spiinos and 'fnxt-mjmediwv ate groovesbetween the splines, having-g stock for grinding throughout length ofthe; splined portion and grindipgiwith a, formed w heeh bearing faces onthe bottoms of said grooves throughout their length andsymmetricallywith reference $0 the axis of 15 the shaft, a

In testimony whereof I afiix my signature in presence of two wiinesses.

FREDERECK ALEXANDER) WARD Witnesses KATHLEEN C, THoMPsoN,

ERNEST PARKER.

